1. Field of the Invention
The invention relates to a drivetrain for a parallel hybrid vehicle, having an internal combustion engine, an electric machine and a transmission.
2. Description of the Related Art
The drivetrain for a parallel hybrid vehicle has an internal combustion engine, an electric machine and a transmission. The internal combustion engine and the electric machine interact with a common input shaft of the transmission. At least one axle of the hybrid vehicle can be driven by the internal combustion engine and/or the electric machine via an output shaft of the transmission. A clutch is between the internal combustion engine and electric machine. The internal combustion engine is decoupled from the input shaft of the transmission when the clutch is open. Thus, the hybrid vehicle is driven by the electric machine alone and the internal combustion engine is stopped. The electric machine spins up the stopped internal combustion engine when the clutch is closed so that the internal combustion engine can be started and can drive the vehicle. The electric machine then either can be shut down or can drive the vehicle together with the internal combustion engine.
The clutch of the above-described parallel hybrid is relatively complex for two reasons. First, the clutch must be very finely controllable so that the electric machine can spin up the stopped internal combustion engine without a jerk occurring in the drivetrain. Second, the clutch must transmit high torques into the drivetrain, in particular in the case of large internal combustion engines. Furthermore, the open clutch must permit high rotational speed differences between its stationary side and its rotating side, so that the electric machine can spin up while the internal combustion engine is stopped.
DE 600 21 163 T2 describes a clutch between a drive input shaft and a drive output shaft of a transmission of a hybrid vehicle for adjusting a transmission torque between the two shafts.
DE 10 2005 038 925 A1 discloses a jaw clutch for an electrically variable transmission for realizing a reverse gear.
DE 10 2007 037 758 A1 proposes a drivetrain for a parallel hybrid vehicle which has only one positively locking clutch.
U.S. 2002/0065168 A1 describes a hybrid vehicle whose transmission has jaw clutches in order to minimize torque fluctuation during gear-changes.
It is an object of the present invention to further develop a drivetrain of the type mentioned in the introduction in such a way that it firstly permits a jerk-free spin-up of the stopped internal combustion engine by means of the electric machine and secondly permits a transmission of high torques of the internal combustion engine into the input shaft of the drivetrain.